In general, a wireless communication system provides a location service for transmitting the location of a mobile terminal to a certain entity periodically or according to a request, by including a relevant function part for calculating the location of the mobile terminal in a network.
A location service-related network structure varies according to an internal network structure such as 3GPP or 3GPP2. Methods for calculating the current location of a mobile terminal include a cell-ID method for transferring an ID of a cell to which the mobile terminal belongs, a method for measuring the time taken for radio waves of the mobile terminal to reach each base station and calculating the location of the mobile terminal by using the trigonometric measurement, and a method for using a global positioning system (GPS).
In order to provide the location service to a user, a considerable of signaling and location information needs to be communicated between the mobile terminal and a location server.
Thus, standard positioning technologies for providing the location service, namely, a location service based on a location of a mobile terminal, have been rapidly spreading. The technologies can be generally provided through a user plane and a control plane. A SUPL (Secure User Plane Location) method is one of the technologies, which provides the location service through the user plane.
The SUPL method is an effective method of transferring location information required for calculating the location of a mobile terminal. That is, in order to provide assistance information such as GPS assistance and in order to bear a position technology-related protocol between the mobile terminal and the network, the SUPL method uses a user plane data bearer.
In a general location information system, the SUPL network related to the location service includes a SUP agent, a SUPL Location Platform (SLP) and a SET (SUPL enabled terminal). The SUPL agent is a logical service access point that uses the actually measured location information. The SLP is a SUPL service access point of a network part for accessing network resources to obtain location information, which calculates an actual location or perform roaming, resource management and the like. The SET is a device which can communicate with the SUPL network using a SUPL interface, and supports definition procedures in the SUPL by interworking with the network via the user plane bearer. For example, the SET can be one of a UE (User Equipment) of UMTS, a MS (Mobile Station) of GSM, a laptop computer having a SET function, or a PDA (Personal Digital Assistants). In the alternative, the SET can be various mobile terminals which are connected through a WLAN (Wireless Local Area Network).
In the location service, a network for which a user has originally registered is called a home network, and when the user moves or roams to an area other than the home network area, the network of that the other area is called a visited network. A SLP in the home network is called an H-SLP (Home-SLP) while a SLP in the visited network is called a V-SLP (Visited-SLP).
When a SUPL procedure starts in the network of the location information system, a SLP to which an external client is first connected is called an R-SLP (Requesting-SLP). The R-SLP is a logical entity, which can be the same as the H-SLP or not. A SET aimed to track its current location is called a target SET.
Two types of the SUPL-based location services are provided, including an area event triggered service which provides a location of a target SET (i.e., mobile terminal) when preset conditions related to a certain area is satisfied, and a periodic triggered service which provides a location of a target SET (i.e., mobile terminal) according to a preset period.
Such two types of SUPL-based location services will now be described in more detail with reference to the drawings.
FIG. 1 is an exemplary view of a periodic triggered service based on a SUPL according to the related art. Hereinafter, each process is described with reference to FIG. 1.
A) A SUPL agent within a SET#1 11 desires to be periodically known of a location of a target SET, namely, SET#2 12. If any data connection is not yet established between the SET#1 11 and a network, the SET#1 11 sets the data connection with the network.
B) The SUPL agent establishes an IP connection with a SLP#1 21 by using a previously received address, and then sends a session start message (e.g., SUPL SET INIT) to establish a session with the SLP#1 21 for the periodic triggered service. Here, the SUPL SET INIT message may include several parameters such as a session-id, an ID of the target SET (i.e., an ID of the SET#2 12), a triggered service mode and trigger information. Here, the triggered service mode parameter indicates whether a service requested is a periodic triggered service or an area event triggered service.
C) The SLP#1 21 receives the SUPL SET INIT message, and searches for a SLP#2 22 which manages the target SET (i.e., the SET#2 12) by using the ID parameter of the target SET included in the SUPL SET INIT message. Here, the SLP#1 21 searches for the SLP#2 22 via a DNS server or other entities.
D) The SLP#1 21 requests the periodic triggered service from the SLP#2 22 managing the target SET (i.e., SET#2 12).
E) In response to the request, the SLP#2 22 check whether or not the SET#1 11 is granted permission to acquire the location of the SET#2 12. The SLP#2 22 then starts the periodic triggered location service for the SET#2 12 according to the request.
F) If information related to a previously measured location exists for the SET#2 12 or a first location measurement (positioning) is completed, the SLP#2 22 sends a response message to the SLP#1 21. Here, the response message includes the location information related to the SET#2 12.
G) Upon receiving the response message, the SLP#1 21 sends a SUPL report message, e.g., SUPL REPORT to the SET#1 11. Here, the SUPL REPORT message includes a position parameter containing the location information related to the SET#2 12. The SUPL REPORT message also includes an index parameter indicating the number of times for positioning and a session-id parameter indicating ID of a session.
H) The SLP#2 22 periodically measures the location of the SET#2 12 according to the request, and then sends the measured location information to the SLP#1 21.
I) The SLP#1 21 sends a SUPL REPORT message including the measured location information to the SET#1 11.
J) Until a termination condition is met, the location of the SET#2 12 is periodically measured, and the measured location information is sent to the SET#1 11.
K) The SLP#2 22 finally measures the location of the SET#2 12, and upon satisfying the termination condition, the SLP#2 22 terminates the periodic triggered location service.
L) The SLP#2 22 sends the finally measured location information to the SLP#1 21.
M) The SLP#1 21 forwards the finally measured location information to the SET#1 11, and simultaneously sends a SUPL END message to the SET#1 11 to inform the end of the periodic triggered location service. Here, the SUPL END message includes a position parameter containing the finally measured location information. The SUPL END message also includes an index parameter indicating the number of times for positioning and the session-id parameter indicating the ID of the session.
After receiving the SUPL END message, then the SET#1 11 releases the IP connection with the SLP#1 21, and releases resources for the session.
As described above, since the SUPL-based periodic triggered service according to the related art is achieved only by a long-term IP connection, the resources of the SET and the network are unnecessarily consumed. That is, the SET#1 11 establishes the IP connection with the SLP#1 21 at the step B). The established IP connection is maintained until the SET#1 11 receives the SUPL END message from the SLP#1 21 at the step M). However, if a considerably long time is spent until the termination condition of the periodic triggered service is satisfied, constantly maintaining the IP connection requires many resources, resulting in a consumption of the resources. In particular, in spite of an intermittent transmission of the measured location information, continuously maintaining the IP connection causes unnecessary consumption of resources. For example, when the location of the SET#2 12 is measured five times at a 10-minute time interval, the measured location information is sent once per 10 minutes. However, even in this case, until measuring the location five times, namely, until 50 minutes elapse, the IP connection remains established, which accordingly causes the consumption of resources. Furthermore, if multiple SETs exist, the SLP#1 21 suffers exhaustion of resources.
In the meantime, FIG. 2 is an exemplary view showing an area event triggered service based on a SUPL according to the related art. Hereinafter, each process is described with reference to FIG. 2.
A) A SUPL agent in a SET#1 11 desires to be known when the location of a SET#2 12 is changed. If any data connection is not yet established between the SET#1 11 and the network, the SET#1 11 performs the data connection with the network.
B) The SUPL agent establishes an IP connection with a SLP#1 21 by using a previously received address, and sends a session start message (e.g., SUPL SET INIT) to the SLP#1 21 to establish a session therewith for an area event triggered service. Here, the SUPL SET INIT message includes parameters such as a session-id, an ID of a target SET (i.e., an ID of SET#212), a triggered service mode, and trigger information. Here, the triggered service mode parameter indicates whether a service requested is a periodic triggered service or an area event triggered service.
C) After receiving the SUPL SET INIT message, the SLP#1 21 searches for a SLP#2 22 managing the target SET (i.e., SET#2 12) by using the ID parameter of the target SET included in the SUPL SET INIT message. Here, the SLP#1 21 searches for the SLP#2 22 via a DNS server or other entities.
D) The SLP#1 21 requests an area event triggered service from the SLP#2 22 managing the target SET (i.e., the SET#2 12).
E) In response to the request, the SLP#2 22 checks whether the SET#1 11 is granted permission to acquire the location of the SET#2 12. Also, the SLP#2 22 starts the area event triggered service for the SET#2 12 according to the request. That is, the SLP#2 22 starts monitoring whether the SET#2 12 moves to another location.
F) Upon starting the area event triggered service, the SLP#2 22 sends a response message to the SLP#1.
G) Upon receiving the response message, the SLP#1 21 sends a SUPL END message to the SET#1 11 to inform that the IP connection and the session do not have to be maintained since the service started. Here, the SUPL END message includes the session-id parameter indicating the session ID. After receiving the SUPL END message, the SET#1 11 releases the IP connection with the SLP#1 21 and releases resources for the session.
H) On the other hand, the SLP#2 22 keeps monitoring whether the location of the SET#2 12 is changed.
I) If the location of the SET#2 12 is changed, the SET#2 12 sends to the SLP#1 21 the measured location information related to the changed location.
J) The SLP#1 21 transfers the measured location information to the SET#1 11. Here, since the connection and the session have already been released, the SLP#1 21 transfers the measured location information according to a WAP PUSH method or a low security method such as an SMS method.
As such, in the SUPL-based area event triggered service according to the related art, the measured location information is transferred via the WAP PUSH method or the low security method such as the SMS method. Accordingly, such information may be exposed externally due to hacking or wrong forwarding, which may cause a severe problem of privacy intrusion.